Electron switching tubes and circuits therefor



March 1952 E. s. RITTNER ETAL 2,588,292

ELECTRON SWITCHING TUBES AND CIRCUITS THEREFOR Filed April 20, 1950 2 SHEETS-SHEET 1 INPUT 56 c I 45 620798 flY/TEL INPUT A IDMMWTZNIE c o-- WRACE JAMZ/ZL HJVZ' IN VEN TORS.

/1M BY AGENT.

E. S- RITTNER ET AL March 4, 1952 ELECTRON SWITCHING TUBES AND CIRCUITS THEREFOR 2 SHEETS-SHEET 2 Filed April 20, 1950 660 m 19. EA Z'DMIMMIZZIZ'IAEE mamas 541140751, 22211 INVENTORS. BY W Patented Mar. 4, 1952 UNITED STATES PATENT OFFICE ELECTRON SWITCHING TUBES AND CIRCUITS THEREFOR son, N. Y.

Application April 20, 1950, Serial No. 156,972

9 Claims. l

The present invention pertains to improvements in electron devices of the type wherein a stream of electrons is caused to impinge on a target of photoconducting semiconductive material whose internal impedance varies as a function of the stream intensity and velocity, and to improved circuit arrangements incorporating such devices.

In the copending application of E. S. Rittner, filed March 29, 1948 and given Serial No. 17,636, issued on February 16, 1951 as Patent No. 2,540,490, there is disclosed electron devices in which an electron beam is directed onto a photoconductive semiconductive element preferably constituted either by silicon, germanium, thallous sulfide, or lead sulfide, these substances each exhibiting a resistivity which depends on the beam intensity and velocity. The principal ob-' ject of the present invention is to provide improved structural arrangements for such devices, as well as new and useful switching circuit embodying said improved devices.

For a complete understanding of the present invention reference is made to the following detailed description thereof to be read in conjunction with the accompanying drawing wherein:

Fig. 1 is a schematic diagram of an electron switching tube circuit in accordance with the invention and in which the photoconducting semiconductive target is illustrated in section.

Fig. 2 is a separate plan view of the target structure.

Fig. 3 is a schematic circuit diagram of an amplifier incorporating an electron device which is energized directly from an alternating-current source.

Fig. 4 is a schematic circuit diagram of a differential amplifier employing a pair of amplifiers of the type disclosed in Fig. 3.

Fig. 5 is a perspective view of the electrodes in another electron device in accordance with the invention,

Fig. 6 is a plan view of the electrode structure shown in Fig. 5,

Fig. 7 is a schematic diagram of a switching system employing a tube of the type disclosed in Figs. 5 and 6, and

Fig. 8 is a perspective view of a modified target structure for a tube of the type disclosed in Fig. 5.

Referring now to Figure 1, there is shown a voltage-responsive switching system including an electron device I0 in accordance with the in-' ventiQn. provided with a cathode-ray gun struc- 2 ture H possessing an intensity-control electrode l2, the cathode-ray beam projected by said gun impinging on a target structure l3 and being defiectable by a pair of electrostatic deflecting plates l4. As shown in Figs. 1 and 2, the targetstructure I3 is formed by a disc-shaped base member [5 of dielectric material along whose circular edge is mounted a pair of arcuately shaped electrodes 16 and I! each having a plu-.

rality of conductive spokes [6a and Ho attached thereto. A hub electrode I8 is afiixed centrally to said base and provided with radial spokes I 8a disposed in intermeshing relationship with,

respect to spokes lBa. and Ila. Coated on the surface of said base in the interstices of spokes Isa, Ila and [8a is a layer IQ of semiconductive material preferably constituted either by germanium, thallous sulfide, silicon or lead sulfide.-

The semiconductive path lying between the spokes on arcuate electrode l1 and hub electrode [8 acts as one arm, and the path lying between the spokes on arcuate electrode I6 and hub elec-- trode It! acts as a second arm in a Wheatstone bridge circuit whose remaining arms are formed by the external resistors 20 and 2|, the latter resistor being variable to effect balancing.

Connected between hub electrode I 8 and the junction of resistors 20 and 2|, which electrode and junction represent the output diagonals of the bridge, is an output resistor 22 whose ends are also connected to output terminals 23. Connected between arcuate electrodes l6 and IT at the input diagonals of the bridge is a direct voltage source 24. Connected between the cathode of the electron gun II and the hub electrode of target [3 is a source of accelerating voltage 25. The control voltage for activating the switching system is applied to the input terminals 26 connected to deflecting plates 14. A bias voltage from a source 21 is applied to intensity control electrode l2 through variable resistor 28.

The behavior of the switching system isas follows: In the absence of a control voltage across the deflecting plates, the beam from gun ll strikes the hub electrode 18, and thereby avoids contact with the semiconductive substance on the-target. Assuming an initial conpressed on a polarized relay to effect: a switching action in a sense dependingon the polarity of the control voltage. resistivity of a particular semiconductive path is altered, and hence the sensitivity of. the. relay, may be controlled by adjusting resistor 28 to obtain a desired beam intensity. It is also to be noted that a modulating signal may be applied to grid i2 whereby the tubeacts' to amplify the signal and then by its switching action. directs it into a desired channel.

Referring. now to Fig. 3,. there is .shownrat switching system employing an electron device 29in which the voltage imposed across the target and the beam accelerating voltage is derived; without rectification, from an. alternating-current source. Electron device 29 includes an in directly heated cathode 30', a control grid 31 and a targetelectrode 32 formed: by a semiconductive substance of the type hereinabove. described in.- terposed between two end terminals.

A transformer is provided having a. primary winding 33, connected at terminals '34-to. an alterhating-current line, a secondary winding 35 connected through an output'resistor 35 acrosssthc. end terminals. of target 3-2,. and a tertiarywinding- 31' arranged in phase opposition towinding 35'and connected between onerterminal of target 321 and cathode 38. A grid leak resistor 38 is connected between grid 3| and cathode 33, a pair ofinput terminals 39 being connected across resistor 38, and a pair of'output terminals 42 being connected across resistor 36.

In operation, a pulsating direct-current component wil appear across resistor 36 whose amplitude will depend on the magnitude of the control voltage impressed on the grid 3!. The voltage established across resistor 36 may be used to actuate a relay, and dueto theincreased amplification afiorded by the electron device, the system is responsive to input control signals of small amplitude. Thus a highly sensitive control device is provided entailinga minimum number of components.

Referring now toFig. 4:, there is disclosed adifierential amplifier employing a pair of elec-- tron devices of the type disclosed in Fig. 3, preferably enclosed in a singleenvelope, whose combined output depends on the relative values of the applied input voltages. As in Fig. 3, the voltages imposed across the targets of the tubes and and the beam accelerating voltages are derived without rectification through a trans former whose primary 42' is connected to an al ternating current source The transformer is provided with a centertapped secondary winding 53; whose ends are connected through resistors 42.: and 45 to. one terminal. of the targets of tubes 48 and ll respectively, .and'whose centertap is connected to the interconnected cathodes of said tubes. Auxiliary secondary windings 36 and i? are provided, one end of each auxiliary secondary being. connected to. a respective; end ofisaidnsem The extent to which the ondary 43, the other end of each auxiliary secondary being connected to the other terminal of a respective target.

The input voltages A and B are applied at terminals 18 and 49 which are connected. respectively across grid resistor 5c and 5| connected between the grid and cathodes of tubes and The voltage developed across resistor 44 is aplied to one primary 52 of an output transformer, and the'voltage developed across resistor is applied to an opposingly wound primary 53 of the transformer. In consequence the average voltage developedin, the secondary 54 represents the differential resultant of the primary voltages.

'3 In operation, since the accelerating voltages applied to the targets of tubes 40 and M are 180 degrees. out of phase, the tubes operate alternately, the voltages developed across resistors 44 and 55 depending on the relative amplitudes of the input voltages A and B respectively. It is to be noted, that in' the control systems disclosed in Figs. 1, 3 and 4, the input circuits are inde:v pendent of the output circuit and no interaction. therebetween can occur.

Another embodiment of an electron, device; is shown in Figs. 5, 6 and 7, the device comprisingin a single envelope, a pair of high-mu 'triodes 55 and 5% and a cone-shaped target constituted by four electrically separated sections 51, .58, 59 and 56'. Triode55 is constituted by a cathode-61, a. grid 62 and an anode 63, and triode 5E by-a cathode 6d, and grid 55 and an anode 56. Connected directly to the anode 63 are apairof: blade-like control electrodesB'l and 68, electrode. 5-! being associated. with target: section: 5.1 andv electrode 68' withsection 58; Similarly. connected directly to anode 56 is a pair of blade-likes oontrol electrodes 59, and 15, electrode; 69 being. associated with target section-59, and electrode iii with section In, Fig: 5, onlyelectrodecB'l is. shown, the others-being omitted for'purposes. of clarity. The target is irradiated; byanelectron beamemittedfrom'a, cylindrical cathode "H, triode. cathodes BI and 64' being mountedonacommonsupport therewith. For purposes of clarity cathode 64 has not'been shown in Fig; 5' 'nor' have the remaining elements of the triode struc tures been included since thesezare conventional.

Each section of the target is formed of nonconductive material and is provided with a; pair of. spaced arcuate terminals 12. and 13, thesurface between the two terminals-being coated'with a semiconductive photoconductive substance of the type described supra. The anode 63 is'connected to one terminalof target section 51 through a high resistance M, said one terminal being connected to the positive pole of a'highvoltage source. The anode 63 is'also connected to one terminal of target section 58 through a high resistance 15, said one terminal being connected' to the positive pole of a high-voltage source.

Anode E6 is connected to one terminal of target section 69 through a high resistance 16, a high positive voltage being applied at this point. Grid 2 is connected to cathode 61 through a grid resistance 13 and a bias battery 86, grid being connected to cathode 64 through agrid resistance is and the same bias battery.

Considering section 5? separatelyun operation, with zero control potential on the grid 52 of tube- 55, electrons from the cathode H strike-the entire surface of section 5's" except for asector in the region of blade electrode 67, which being at a lower potential than the target section because of the voltage drop across resistance 14 acts as a shield. When however, a negative control potential is applied to grid 62, the anode current is reduced with a resultant decrease in the voltage drop across resistances M and 15, thereby reducing the sector of the target section 5! which is not'irradiated. Thus as the shielded sector on the target section varies with the control voltage applied to grid 62, the internal resistance of the target section is accordingly altered. Blade 68 has the same control influence on section 58. The same efiect is experienced with respect to the influence of a control voltage on grid 65 on the internal resistance of sections 59 and 50.

This effect may be used for example to prov de a double pole double throw switching action by applying the signal to be switched to terminals 8!, one of which is connected to one arcuate terminal of both sections 5'! and 59, and the other of which is connected to one arcuate terminal of sections 58 and 68. The other arcuate terminals of sections 5! and 58 are connected to one pair of output terminals 33 while the other arcuate terminals of sections 59 and '60 are connected to output terminals 85.

By applying a negative control voltage to terminals 82 connected to grid E2, the signal to be switched is fed to output terminals 83 and by applying a negative control voltage to terminals 84 connected to grid 65, the signal to be switched is fed to output terminal 85. While there has been shown a target arrangement employing four sections, it is obvious that a greater number may be used in conjunction with blade electrodes coupled to the anodes of amplifier tubes to effect more complex switching functions.

By using a conically-shaped target the formation of a sensitive layer on the inner surface thereof is greatly facilitated. This is acccmplished by inverting the cone and applying the material by vacuum evaporation. Preferably the cathode is protected by a small cap (not shown) attached to the end of the support. The conical target structure shown in Fig. 5 may be replaced by one of tubular shape, as illustrated in Fig. 8 or by other shapes if desired. While the terminals T2 and 13 in Fig. 5 are shown in circumferential positions, it is to be understood that radially disposed terminals may alternatively be employed, in which case should the sensitive area intermediate the terminals not be irradiated then the resistance therebetween would effectively constitute an open circuit. Similarly in the tar-- get shown in Fig. 8, the terminals may be arranged either longitudinally or circumferentially. It is also to be noted that several targets may be contained in a common envelope.

While there have been shown what at present are considered preferred embodiments of the invention, it will be evident that many changes and modifications may be made therein without departing from the essence of the invention, and it is intended in the annexed claims to cover all such changes and modifications as fall within the scope and true spirit of the invention.

What is claimed is:

1. An electron switching device comprising a cathode-ray gun for generating an electron beam. a target structure positioned to intercept said beam and including a pair of spaced end terminals, a hub terminal positioned intermediate said end terminals and an active element interconnecting said hub terminal and said end terminals to define first and second control paths, said element being formed of semiconductive photoconductive material, and means to deflect said beam across said target structure whereby the internal resistance of the impinged path is varied by said beam.

2. An electron switching device comprising a cathode-ray gun for generating an electron beam and provided with a control electrode to control the density of said beam, a target structure positioned to intercept said beam and including a pair of spaced end terminals, a hub terminal positioned intermediate said end terminals and an active element interconnecting said hub terminal and said end terminals to define firstand second control paths, said element being formed of semiconductive photoconductive material selected from group IV of the periodic table, and means to deflect said beam to impinge selectively on one of said paths, whereby the internal resistance of the impinged path is varied by said beam.

3. An electron switching device comprising a cathode-ray gun for generating an electron beam, a target structure positioned to intercept said beam and including a pair of spaced end terminals, a hub terminal interposed between said end terminals and an active element interconnecting said hub and said end terminals to define first and second control paths, said element being formed of thallous sulfide, and means to deflect said beam to impinge selectively on one of said paths, whereby the internal resistance of the impinged path is varied by said beam.

4. An electronic switching circuit comprising an electron device including a cathode-ray gun for generating an electron beam, a target structure positioned to intercept said beam and including a pair of spaced end terminals, a hub terminal interposed between said end terminals and an active element interconnecting said hub terminal and said end terminals to define first and second control paths, said element being formed of semiconductive photoconductive material and means to deflect said beam to impinge selectively on one of said paths, a Wheatstone bridge including first and second resistances connected in series across the end terminals of said target structure and an output resistance connected between the hub terminal and the junction of said first and second resistances, and means to apply a control voltage to said deflecting means.

5. An electronic switching circuit comprising an electron device including a cathode-ray gun for generating an electron beam, a. target structure positioned to intercept said beam and including a pair of spaced end terminals, a hub terminal interposed between said end terminals and an active element interconnecting said hub terminal and said end terminals to define first and second control paths, said element being formed of semiconductive photoconductive material and means to deflect said beam to impinge selectively on one of said paths, a Wheatstone bridge including first and second resistances conto interceptrsaid-' eamtand nclud n a pa r Q spaced end terminals, hub terminal interposed between said end terminals and an active, element; interconnectingsaid hub terminal and; said end terminals to define first and second control paths, said element being formed of thallous sulfide, and means to defiectsaid beam across; said, target structure, a Wheatstone bridge including first. and second resistances connected in series across. the end terminals of said target structure and an output resistance connected between the hub ter-. minal and the juncture of said first, and second resistances,,and means to apply a control voltage to said deflecting; means.

7; In an electron switching device, a; target structure comprising a circular insulating disc, a pair of arcuate terminals mounted on the op, posing edges of said disc, a hub terminal mounted centrally on said disc, and an active element con,- stituted by a semiconductive photoconductive material coated on the surface of said, disc be-. tween said hub terminalv and. said .arcuate. tierminals.

8. In an electron switching device, a target 7 rality of radial spokes, a hub terminal mounted centrally on said disc, and provided with a; plu-. rality of radial spokes disposed in intermeshing 1 relationship with the arcuate: terminal spokes,

and an active element coated on the surface of said disc *betweensaid spokes, said elementbelng, constituted by asemiconductive, photoconductive,

material.

' 9. An arrangement, asset forth in claim-8, wherein said material is constituted by, lead sul=- fideu.

EDMUND S. RI'ITNER. FRANK E. GRACE. SAMUEL FINE. GEORGE A., BEUTEL.

REFERENCES CITED The following references; are of, record in the,

file of this .patent:

Crystal Counters, Robert Hofstadter, Nucle onics, Apr. 1949, pgs. 2-27, published by McGraw- Hill.

The Crystal Counter, Utrecht Dissertation (1945) by P., J. Van Heerd na 

